<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        span {
            width: 100px;
            text-align: justify;
            float: left;
        }

        span:after {
            content: '.';
            width: 100%;
            display: inline-block;
            overflow: hidden;
            height: 0;
        }

        input {
            width: 100px;
        }
    </style>
</head>

<body>
    <div class="demo">
        <span>昵称</span>：<input type="text" style='width: 100px'><br><br>
        <span>电子邮箱</span>：<input type="email" style='width: 100px;'>
    </div>
</body>

</html>